The goal of this proposal is to develop new selective chemical methods for achieving selective dihalogenation, halofunctionalization, and dihalide derivatization reactions that can be used for the synthesis of complex, biologically active small molecules. Nearly 2,000 compounds containing either a chlorine- or bromine-bearing stereogenic center have been characterized, and while biological activity has been demonstrated in areas of pressing medical need (e.g. anticancer, antibiotic), further investigation into the therapeutic potential and physical basis for bioactivity has been hindered by an unreliable supply from natural sources as well as by a lack of selective methods for systematic chiral organohalogen synthesis. Preliminary findings indicate that the modular combination of metal Lewis acid, electrophilic halogenating agent, and ligand is capable of effecting selective dibromination, bromochlorination, dichlorination, and haloetherification on a variety of alcohol-containing alkene substrates. The first aim of this research is the full development of this strategy to catalyst-controlled chemo-, regio-, diastereo-, and enantioselective dihalogenation and halofunctionalization reactions. The second aim of this research is the extension of this strategy for the synthesis of halogenated bioactive small molecules. The third aim of this research involves identifying conditions that will allow for the derivatization of enriched dihalides for the selective synthesis of bioactive small molecules through stereospecific carbon-heteroatom and carbon-carbon bond-forming reactions. This contribution is significant because it will enable the selective preparation of numerous classes of chiral halogenated and non-halogenated compounds for further biological evaluation. Innovation stems from developing a general, tunable, methodological platform to enable the predictable and selective preparation of numerous classes of chiral halogenated small molecules.